This invention provides a superheated steam apparatus that is cable of efficiently heating water to generate superheated steam, and to perform a process such as sterilization utilizing this superheated steam while keeping the loss of heating energy to a minimum. The invention comprises a processing section 11 at the top on the inside of a housing container 2, which is at atmospheric pressure, for performing a process utilizing superheated steam, and where the processing section 11 includes a steam discharge outlet 12, and a superheated steam generation section 10 located at the bottom of the processing section 11; and where the superheated steam generation section 10 generates superheated steam or moist air inside the housing container 2, hat is essentially in an open state, and is connected with the processing section 11 in an open state.